This study analyzed the data on gingival bleeding, calculus, and periodontal attachment loss in 14-17 year-old children who participated in the National Survey of Oral Health in U.S. School Children conducted by the NIDR during 1986-87. The 11,111 children in the sample represent an estimated 13 million U.S. school children in this age group. The prevalence of gingivitis was approximately 60% for children in this age group. The percent of examined sites with gingivitis per child, however, was less than 6%. There was an overall age associated decline in prevalence of gingivitis. Males, in general, and children in the category of "blacks and other races" showed higher prevalence of gingivitis. Prevalence of gingivitis was slightly higher at buccal than mesial sites and was most common in molar areas in the maxilla and incisor areas in the mandible. The prevalence of supragingival calculus alone was nearly 34% and subgingival calculus was approximately 23%. The percent of teeth with calculus per child was approximately 8 for the former and 4 for the latter type of calculus. There was a slight age-associated increase in prevalence of latter type of calculus. Males and children in the category of "blacks and other races" showed higher prevalence of both types of calculus. The Mean periodontal attachment loss, determined by probing with #2-12 probe, was 0.33 mm (0.26 mm for buccal and 0.40 mm for mesial surfaces) and varied very little by age, sex or race. The teeth most frequently affected by attachment loss of 2 mm or more were maxillary molars and bicuspids, followed by mandibular molars and cuspids.